T Green Sea Turtle Chelonia mydas

Transcription

Green Sea Turtle
Chelonia mydas
T
he green sea turtle nests regularly in South Florida,
predominantly on the east coast between Volusia and
Broward counties. The green sea turtle accounts for
about 1.9 percent of total nesting reported statewide. The
green turtle nesting and hatching season in South Florida
Critical Habitat: Designated (September 1998):
Waters of Culebra Island, Puerto extends from May through November. Sea turtles, in
Rico, and its outlying keys.
general, are susceptible to anthropogenic impacts in the
marine environment, as well as on their nesting beaches.
Florida Status:
Endangered
This account provides an overview of the biology of the
Recovery Plan Status: Contribution: May 1999
green sea turtle throughout its range. The discussion of
Geographic Coverage: South Florida
environmental threats and management activities, however,
pertains only to South Florida. Serious threats to the green
Figure 1. Florida nesting distribution of the green sea turtle on South Floridas nesting beaches include:
artificial lighting, beach nourishment, beach armoring,
sea turtle.
increased human presence, and exotic beach and dune
vegetation.
This account is modified from the 1991 Recovery Plan
for the U.S. Population of Atlantic Green Turtle and
represents South Floridas contribution to the range-wide
recovery plan for this species (NMFS and FWS 1991).
Federal Status:
Endangered (Florida, Pacific
coast of Mexico; July 28, 1978)
Threatened (except as above;
July 28, 1978)
Description
The green turtle is among the largest of the sea turtles;
adults commonly reach 1 m in carapace length and 150 kg
in mass. The mean size of female green turtles nesting in
Florida is 1.5 m standard straight carapace length and 136.1
kg body mass (Witherington and Ehrhart 1989). Hatchling
green turtles weigh approximately 25 g, and the carapace is
about 50 mm long. The dorsal surface is black, and the
ventral surface is white. The plastron of Atlantic green
turtles remains a yellowish white throughout life, but the
carapace changes in color from solid black to a variety of
shades of grey, green, brown and black in starburst or
irregular patterns.
Characters that distinguish the green turtle from other
sea turtle species are a smooth carapace with four pairs of
lateral (or costal) scutes and a single pair of elongated
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GREEN SEA TURTLE
Multi-Species Recovery Plan for South Florida
prefrontal scales between the eyes. The nuchal scute does not touch the first
costal scute and the inframarginal scutes do not have pores. Each flipper has a
single claw and the carapace is oval-shaped and depressed. The crawls of
nesting green turtles are deeply cut, with symmetrical diagonal marks made by
the front flippers (Pritchard et al. 1983).
Taxonomy
The green sea turtle was described by Linnaeus in 1758 as Testudo mydas with
Ascension Island as the type locality. Schweigger first applied the binomial we
use today, Chelonia mydas, in 1812. The taxonomic status of the green turtle is
not clear. There is believed to be little genetic exchange among isolated
breeding colonies, and, thus, these colonies may deserve sub-specific
recognition. Although trinomials have been applied to various populations in
the past, they are generally not in use today. Advances in DNA research are
helping to solve these taxonomic questions by identifying genetically isolated
populations. For a complete discussion of the systematics of green turtles, see
Pritchard and Trebbau (1984) and Hirth (1980a).
Distribution
The green sea turtle is a circum-global species in tropical and sub-tropical
waters. The worldwide distribution of green turtles has been described by
Groombridge (1982). In the U.S., green turtles are found around the U.S.
Virgin Islands and Puerto Rico, and in the continental U.S. from Texas to
Massachusetts. Areas that are known as important feeding areas for green
turtles in Florida include: Indian River Lagoon, the Florida Keys, Florida Bay,
Homosassa River, Crystal River and Cedar Key.
Major green turtle nesting colonies in the Atlantic occur on Ascension
Island, Aves Island, Costa Rica and Surinam. In U.S. Atlantic waters, green
turtles nest in small numbers in the U.S. Virgin Islands and in Puerto Rico.
Although they nest in all coastal counties in South Florida (Figure 1), the
largest nesting occurs along the east coast of Florida, particularly in Brevard,
Indian River, St. Lucie, Martin, Palm Beach and Broward counties. Nesting
along the southwest coast of Florida was documented for the first time in 1994
(Foley 1997).
Habitat
Green turtles occupy three habitat types: high-energy oceanic beaches,
convergence zones in the pelagic habitat, and benthic feeding grounds in
relatively shallow, protected waters. Females deposit egg clutches on highenergy beaches, usually on islands, where a deep nest cavity can be dug above
the high water line. Hatchlings leave the beach and apparently move into
convergence zones in the open ocean where they spend an undetermined length
of time (Carr 1986). When turtles reach a carapace length of approximately 20
to 25 cm, they leave the pelagic habitat and enter benthic feeding grounds.
These foraging habitats are commonly pastures of seagrasses and/or algae, but
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GREEN SEA TURTLE
Green sea turtle.
Original photograph courtesy of
U.S. Fish and Wildlife Service.
small green turtles can also be found over coral reefs, worm reefs, and rocky
bottoms. Some feeding grounds only support certain size classes of green
turtles; the turtles apparently move among these foraging areas--called
developmental feeding grounds--as they grow. Other feeding areas, such as
Miskito Cays, Nicaragua, support a complete size range of green turtles from
20 cm to breeding adults. Coral reefs or rocky outcrops near feeding pastures
are often used as resting areas, both at night and during the day.
Critical Habitat
Critical habitat was designated for the green sea turtle in September 1998.
Although this designation does not include Florida, is does include the waters
of Culebra Island, Puerto Rico, and its outlying keys. Critical habitat for green
sea turtles identifies specific areas which have those physical or biological
features essential to the conservation of the green sea turtle and/or may require
special management considerations.
Behavior
The discussion of behavior in this account is brief. Several excellent reviews
of the biological characteristics of green turtles that have been published in
recent years include Hirth 1980a, Groombridge 1982, Ogren 1984, Pritchard
and Trebbau 1984, and Ehrhart and Witherington 1992.
Reproduction and Demography
Female green turtles emerge on nesting beaches at night to deposit eggs; the
process takes an average of two hours. Descriptions of the behavioral
sequences have been reviewed by Ehrhart (1982). From one to seven clutches
are deposited within a breeding season at 12 to 14 day intervals. The average
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number is usually given as two to three clutches (Carr et al. 1978), but accurate
data on the number of clutches deposited per season are difficult to obtain.
Mean clutch size is usually 110 to 115 eggs, but this average varies among
populations. Average clutch size reported for Florida was 136 eggs in 130
clutches (Witherington and Ehrhart 1989). Only occasionally do females
produce clutches in successive years. Usually 2 to 4, or more years intervene
between breeding seasons. Mating occurs in the water off the nesting beaches.
Very little is known about the reproductive biology of males, but it is thought
that males may migrate to the nesting beach every year (Balazs 1983).
Hatching success of undisturbed nests is usually high, but on some beaches,
predators destroy a high percentage of nests (Stancyk 1982). Large numbers of
nests are also destroyed by inundation and erosion. Temperature-dependent sex
determination has been demonstrated for green turtles (see review in Standora
and Spotila 1985). Eggs incubated below a pivotal temperaturewhich may
vary among populationsproduce primarily males, and eggs incubated above
the pivotal temperature produce primarily females. Reviews of the
reproductive biology of green turtles can be found in Hirth (1980b), Ehrhart
(1982) and Bjorndal and Carr (1989).
Growth rates of pelagic-stage green turtles have not been measured under
natural conditions. However, growth rates of green turtles have been measured
on the benthic feeding grounds. Green turtles grow slowly. In the southern
Bahamas, green turtles grew from 30 to 75 cm in 17 years, and growth rate
decreased with increasing carapace length (Bjorndal and Bolten 1988). Growth
rates measured in green turtles from Florida (Frazer and Ehrhart 1985), U.S.
Virgin Islands (Boulon and Frazer 1990) and Puerto Rico (Collazo et al. 1992)
fall within the range of growth rates measured in the southern Bahamas
(Bjorndal and Bolten 1988). Based on growth rate studies of wild green turtles,
estimates of age at sexual maturity range from 20 to 50 years (Balazs 1982,
Frazer and Ehrhart 1985).
Migration
The navigation feats of the green turtle are well known, but poorly understood.
We know that hatchlings and adult females on the nesting beach orient toward
the ocean using photic cues (Ehrenfeld 1968, Mrosovsky and Kingsmill 1985).
We do not know what cues are employed in pelagic movements, in movements
among foraging grounds, or in migrations between foraging grounds and
nesting beaches. Because green turtles nest on high energy beaches and feed in
quiet, low-energy marine pastures, these areas tend to be located some distance
apart. Green turtles that nest on Ascension Island forage along the coast of
Brazil, some 1,000 km away (Carr 1975). Genetic analysis using restriction
fragment analysis and direct sequencing of mitochondrial DNA have shown
that green turtles return to nest on their natal beaches (Allard et al. 1994,
Bowen et al. 1989, Bowen et al. 1992, Meylan et al. 1990).
Foraging
It is assumed that post-hatchling, pelagic-stage green turtles are omnivorous,
but there are no data on diet of this age class. It is known that once green turtles
shift to benthic feeding grounds they are herbivores. They feed on both
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seagrasses and algae. Information on diet and nutrition of green turtles has
been reviewed (Mortimer 1982a, Bjorndal 1985). The location of the foraging
grounds of green turtles that nest in Florida is not known.
A population of juvenile green turtles (2-60 kg) forage as herbivores in the
central Indian River Lagoon near Sebastian (Ehrhart et al. 1986), from
Mosquito Lagoon in Brevard County south to Palm Beach County, and along
coastal areas of Sabelleriid worm reefs and anastasia rock (A. Meylan, DEP,
personal communication 1998). Post-nesting females have recently been
tracked by satellite telemetry from the beaches of the Archie Carr NWR to the
shallow, benthic habitats of the Florida Keys (P. Tritaik, FWS, personal
communication 1998).
Relationship to Other Species
In South Florida, the green sea turtle shares nesting beaches with the threatened
loggerhead sea turtle (Caretta caretta) in every county where it nests, and with
the endangered leatherback sea turtle (Dermochelys coriacea), most commonly
in Martin and Palm Beach counties. Other federally listed species that occur in
coastal dune and coastal strand habitat, and that need to be considered when
managing nesting beaches, are the southeastern beach mouse (Peromyscus
polionotus niveiventris) and the beach jacquemontia (Jacquemontia reclinata).
Beach nourishment projects, in particular, could affect these species as well as
the turtles. The range of the beach mouse in South Florida is estimated to
include Indian River County south to Broward County. The beach
jacquemontia is found in Palm Beach County south to Miami, Miami-Dade
County.
A variety of natural and introduced predators, such as raccoons (Procyon
lotor), feral hogs, foxes, ants, and ghost crabs prey on incubating eggs and
hatchling sea turtles. The principal predator of sea turtle eggs, the raccoon, may
take up to 96 percent of all eggs in nests deposited on a beach (Davis and
Whiting 1977, Hopkins and Murphy 1980, Stancyk et al. 1980, Talbert et al.
1980, Schroeder 1981, Labisky et al. 1986). In 1996, Hobe Sound NWR
experienced depredation in 23 percent of the nests enumerated (FWS 1996). In
addition to the destruction of eggs, certain predators may take considerable
numbers of hatchlings just prior to or upon emergence from the sand.
Predation of hatchling and very young turtles is assumed to be significant
and predation of subadult through adult stage turtles is assumed less common,
but valid estimates of mortality due to predation at various life history stages
are extremely difficult, if not impossible, to obtain and have not been
determined. Hatchlings entering the surf zone and pelagic stage hatchlings may
be preyed upon by a wide variety of fish species and, to a lesser extent, marine
birds. Stancyk (1982) in an extensive literature review reported predators of
juvenile and adult turtles to include at least six species of sharks, killer whales,
bass, and grouper. Tiger sharks appear to be the principal predator of subadult
and adult turtles. While stranded turtles may exhibit shark-inflicted injuries,
caution must be exercised in attributing a cause of death, as these wounds can
be inflicted postmortem.
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Table 1. Average number
of green sea turtle nests
by county from 1985 to
1995.
County
Average
Indian River
55
St. Lucie
48
Martin
163
Palm Beach
301
Broward
58
Miami-Dade
4.5
Monroe
6.5
Collier*
9
Lee**
3.5
Charlotte*
9
Sarasota*
5
*Nesting activity reported
from 1994 only
**Nesting activity reported
from 1994-1995 only
Status and Trends
The green turtle is listed as endangered by the International Union for
Conservation of Nature and Natural Resources (IUCN) and is listed on
Appendix I of the Convention on International Trade in Endangered Species of
Wild Fauna and Flora (CITES). On July 28, 1978 (43 FR 32800), under the
U.S. Endangered Species Act of 1973, the green sea turtle was listed as
threatened except for the breeding populations in Florida and on the Pacific
coast of Mexico, where they were listed as endangered. Green turtles continue
to be heavily exploited by man, and degradation of nesting and feeding habitats
is a serious problem. Overexploitation by man has already caused the
extinction of large green turtle populations, including those that once nested on
Bermuda and the Cayman Islands. The status of green turtle populations is
difficult to determine because of the long generation time and inaccessibility of
early life stages. The number of nests deposited in Florida appears to be
increasing, but whether this upward trend is due to an increase in the number
of nests or is a result of more thorough monitoring of the nesting beaches is
uncertain.
The following discussion of sea turtle nesting within the South Florida
Ecosystem, as well as comparisons to statewide nesting trends, was derived
from data provided by Meylan et al. (1995) and DEP (1996).
Statewide, green sea turtle nests amounted to 1.9 percent of total sea turtle
nesting during 1979 to 1992. From 1988 to 1992, while survey efforts
remained relatively constant, the total number of reported green sea turtle nests
statewide fluctuated between 455 and 2,509. In addition, it appears that green
sea turtle nesting exhibits a 2-year cycle in activity. Although Meylan et al.
(1995) report that an increase in green sea turtle nesting has been observed
statewide, the reason for this increase is unknown and is regarded with cautious
optimism.
Although the majority of green turtle nesting occurred in Brevard County
(39.5 percent), just outside of the South Florida Ecosystem, Palm Beach
County supported the second highest percentage of green turtle nests during
that period with 23.1 percent of nests. The average number of nests that
annually occur within the South Florida Ecosystem are shown in Table 1.
Although the green sea turtle nests in all coastal counties in South Florida,
these data show that Palm Beach County is clearly the most important nesting
location. We chose to only represent the past 10 years of survey data in Table 1,
because there was less beach surveyed and the data were not complete prior to
1985. In addition, nesting along the southwest coast of Florida was
documented for the first time in 1994 (Foley 1997).
Environmental Threats
A number of threats exist to sea turtles in the marine environment, including:
oil and gas exploration, development, and transportation; pollution; trawl,
purse seine, hook and line, gill net, pound net, longline, and trap fisheries;
underwater explosions; dredging; offshore artificial lighting; power plant
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entrapment; entanglement in debris; ingestion of marine debris; marina and
dock development; boat collisions; and poaching. These threats and protective
measures are discussed in detail in the Recovery Plan for U.S. Population of
the Atlantic Green Turtle (NMFS and FWS 1991). In South Florida, and for
this recovery plan, we are focusing on the threats to nesting beaches, including:
beach erosion, armoring, and nourishment; artificial lighting; beach cleaning;
increased human presence; recreational beach equipment; exotic dune and
beach vegetation; nest loss to abiotic factors; and poaching.
Beach Erosion: Erosion of nesting beaches can result in partial or total loss
of suitable nesting habitat. Erosion rates are influenced by dynamic coastal
processes, including sea level rise. Mans interference with these natural
processes through coastal development and associated activities has resulted in
accelerated erosion rates and interruption of natural shoreline migration
(National Research Council 1990).
Beach Armoring: Where beachfront development occurs, the site is often
fortified to protect the property from erosion. Virtually all shoreline
engineering is carried out to save structures, not dry sandy beaches, and
ultimately results in environmental damage. One type of shoreline engineering,
collectively referred to as beach armoring, includes sea walls, rock revetments,
riprap, sandbag installations, groins, and jetties. Beach armoring can result in
permanent loss of a dry nesting beach through accelerated erosion and
prevention of natural beach/dune accretion and can prevent or hamper nesting
females from accessing suitable nesting sites. Clutches deposited seaward of
these structures may be inundated at high tide or washed out entirely by
increased wave action near the base of these structures.
As these structures fail and break apart, they spread debris on the beach
trapping both adults and hatchlings, impede access to suitable nesting areas and
cause higher incidences of false crawls (non-nesting emergences). Sandbags
are particularly susceptible to rapid failure and result in extensive debris on
nesting beaches. Rock revetments, riprap, and sandbags can cause nesting
turtles to abandon nesting attempts or to construct improperly sized and shaped
egg cavities when inadequate amounts of sand cover these structures.
Information obtained during preparation of the sea turtle recovery plans
indicated that approximately 21 percent (234 km) of Floridas beaches were
armored at that time (NMFS and FWS 1991).
Groins and jetties are designed to trap sand during transport in longshore
currents or to keep sand from flowing into channels in the case of the latter.
These structures prevent normal sand transport and accrete beaches on one side
of the structure while starving neighboring beaches on the other side, thereby
resulting in severe beach erosion (Pilkey et al. 1984) and corresponding
degradation of suitable nesting habitat.
Drift fences, also commonly called sand fences, are erected to build and
stabilize dunes by trapping sand moving along the beach and preventing
excessive sand loss. Additionally, these fences can serve to protect dune
systems by deterring public access. Constructed of narrowly spaced wooden or
plastic slats or plastic fabric, drift fences when improperly placed can impede
nesting attempts and/or trap emergent hatchlings and nesting females.
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Beach Nourishment: Beach nourishment consists of pumping, trucking, or
scraping sand onto the beach to rebuild what has been lost to erosion. Although
beach nourishment may increase the potential nesting area, significant adverse
effects to sea turtles may result if protective measures are not taken. Placement
of sand on an eroded section of beach or an existing beach in and of itself may
not provide suitable nesting habitat for sea turtles. Beach nourishment can
impact turtles through direct burial of nests and by disturbance to nesting
turtles if conducted during the nesting season. Beach nourishment may result
in changes in sand density (compaction), beach shear resistance (hardness),
beach moisture content, beach slope, sand color, sand grain size, sand grain
shape, and sand grain mineral content if the placed sand is dissimilar from the
original beach sand (Nelson and Dickerson 1988a). These changes can affect
nest site selection, digging behavior, incubation temperature (and hence sex
ratios), gas exchange parameters within incubating nests, hydric environment
of the nest, hatching success, and hatchling emerging success (Mann 1977,
Ackerman 1980, Mortimer 1982b, Raymond 1984a).
Beach compaction and unnatural beach profiles that may result from beach
nourishment activities could adversely affect sea turtles regardless of the
timing of the projects. Very fine sand and/or the use of heavy machinery can
cause sand compaction on nourished beaches (Nelson et al. 1987, Nelson and
Dickerson 1988a). Significant reductions in nesting success have been
documented on severely compacted nourished beaches (Raymond 1984a).
Increased false crawls result in increased physiological stress to nesting
females. Sand compaction may increase the length of time required for female
sea turtles to excavate nests, also causing increased physiological stress to the
animals (Nelson and Dickerson 1988c). Nelson and Dickerson (1988b)
evaluated compaction levels at 10 renourished east coast Florida beaches and
concluded that 50 percent were hard enough to inhibit nest digging, 30 percent
were questionable as to whether their hardness affected nest digging, and 20
percent were probably not hard enough to affect nest digging. They further
concluded that, in general, beaches nourished from offshore borrow sites are
harder than natural beaches, and, while some may soften over time through
erosion and accretion of sand, others may remain hard for 10 years or more.
On nourished beaches, steep escarpments may develop along their water
line interface as they adjust from an unnatural construction profile to a more
natural beach profile (Coastal Engineering Research Center 1984, Nelson et al.
1987). These escarpments can hamper or prevent access to nesting sites.
Female turtles coming ashore to nest can be discouraged by the formation of
an escarpment, leading to situations where they choose marginal or unsuitable
nesting areas to deposit eggs (e.g., in front of the escarpments, which often
results in failure of nests due to repeated tidal inundation). Escarpments may
also form during turtle nesting season postnourishment, which creates a
seemingly safe place for nesting turtles, only to be washed out (DEP personal
communication 1998). This effect can be minimized by leveling the beach
prior to the nesting season.
A change in sediment color due to beach nourishment could change the
natural incubation temperatures of nests. This, in turn, could alter natural sex
ratios. To provide the most suitable sediment for nesting sea turtles, the color
of the nourished sediments must resemble the natural beach sand in the area.
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Natural reworking of sediments and bleaching from exposure to the sun would
help to lighten dark nourishment sediments; however, the time frame for
sediment mixing and bleaching to occur could be critical to a successful sea
turtle nesting season.
Nourishment projects result in heavy machinery, pipelines, increased
human activity, and artificial lighting on the project beach. These activities are
normally conducted on a 24-hour basis and can adversely affect nesting and
hatching activities. Pipelines and heavy machinery can create barriers to
nesting females emerging from the surf and crawling up the beach, causing a
higher incidence of false crawls and an unnecessary energy expenditure.
Increased human activity on the project beach at night may cause further
disturbance to nesting females. Artificial lights along the project beach and in
the nearshore area of the borrow site may deter nesting females and disorient
or misorient emergent hatchlings from adjacent non-project beaches.
Beach nourishment projects require continual maintenance (subsequent
nourishment) as beaches erode, therefore their negative impacts to turtles are
repeated on a regular basis. Nourishment of highly eroded beaches (especially
those with a complete absence of dry beach) can be beneficial to nesting turtles
if conducted properly. Careful consideration and advance planning and
coordination must be carried out to ensure timing, methodology, and sand
sources are compatible with nesting and hatching requirements.
Artificial Lighting: Extensive research has demonstrated that the principal
component of the sea-finding behavior of emergent hatchlings is a visual
response to light (Daniel and Smith 1947, Hendrickson 1958, Carr and Ogren
1960, Ehrenfeld and Carr 1967, Dickerson and Nelson 1989, Witherington and
Bjorndal 1991). Artificial beachfront lighting from buildings, streetlights, dune
crossovers, vehicles, and other types of beachfront lights have been
documented in the disorientation (loss of bearings) and misorientation
(incorrect orientation) of hatchling turtles (McFarlane 1963, Philibosian 1976,
Mann 1977, Ehrhart 1983).
The results of disorientation or misorientation are often fatal. Many
lighting ordinance requirements do not become effective until 11 p.m., whereas
over 30 percent of hatchling emergence occurs prior to this time (Witherington
et al. 1990). As hatchlings head toward lights or meander along the beach, their
exposure to predators and likelihood of desiccation is greatly increased.
Misoriented hatchlings can become entrapped in vegetation or debris, and
many hatchlings are found dead on nearby roadways and in parking lots after
being struck by vehicles. Hatchlings that successfully find the water may be
misoriented after entering the surf zone or while in nearshore waters. Intense
artificial lighting can even draw hatchlings back out of the surf (Daniel and
Smith 1947, Carr and Ogren 1960). During the period 1989 to 1990, a total of
37,159 misoriented hatchlings were reported to the Florida Department of
Natural Resources (now DEP). Undoubtedly a large but unquantifiable number
of additional misorientation events occurred but were not documented due to
obliteration of observable sign, depredation, entrapment in thick vegetation,
loss in storm drains, or obliteration of carcasses by vehicle tires.
The problem of artificial beachfront lighting is not restricted to hatchlings.
In June 1992, a nesting loggerhead was killed by an automobile as it wandered
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onto Highway AlA at Patrick Air Force Base in Cocoa Beach, Florida,
misoriented by lights from the west side of the highway. Raymond (1984a)
indicated that adult loggerhead emergence patterns were correlated with
variations in beachfront lighting in south Brevard County, Florida, and that
nesting females avoided areas where beachfront lights were the most intense.
Witherington (1992) found that both green and loggerhead sea turtles showed
a significant tendency to avoid stretches of beach lighted with white mercuryvapor luminaires. Witherington (1986) noted that loggerheads aborted nesting
attempts at a greater frequency in lighted areas. Problem lights may not be
restricted to those placed directly on or in close proximity to nesting beaches.
The background glow associated with intensive inland lighting, such as that
emanating from nearby large metropolitan areas, may deter nesting females
and disorient or misorient hatchlings navigating the nearshore waters.
Cumulatively, along the heavily developed beaches of the southeastern U.S.,
the negative effects of artificial lights are profound.
Beach Cleaning: Beach cleaning refers to the removal of both abiotic and
biotic debris from developed beaches. There are several methods employed
including mechanical raking, hand raking, and picking up debris by hand.
Mechanical raking can result in heavy machinery repeatedly traversing nests
and potentially compacting sand above nests. Resulting tire ruts along the
beach may hinder or trap emergent hatchlings. Mann (1977) suggested that
mortality within nests may increase when externally applied pressure from
beach cleaning machinery is common on soft beaches with large grain sand.
Mechanically pulled rakes and hand rakes can penetrate the surface and disturb
the sealed nest or may actually uncover pre-emergent hatchlings near the
surface of the nest. In some areas, collected debris is buried directly on the
beach, and this can lead to excavation and destruction of incubating egg
clutches. Disposal of debris near the dune line or on the high beach can cover
incubating egg clutches and subsequently hinder and entrap emergent
hatchlings and may alter natural nest temperatures.
Increased Human Presence: Residential and tourist use of developed (and
developing) nesting beaches can result in negative impacts to nesting turtles,
incubating egg clutches and hatchlings. The most serious threat caused by
increased human presence on the beach is the disturbance to nesting females.
Nighttime human activity can cause nesting females to abort nesting attempts
at all stages of the behavioral process. Murphy (1985) reported that disturbance
can cause turtles to shift their nesting beaches, delay egg laying, and select
poor nesting sites. Heavy utilization of nesting beaches by humans (pedestrian
traffic) may result in lowered hatchling emerging success rates due to
compaction of sand above nests (Mann 1977), and pedestrian tracks can
interfere with the ability of hatchlings to reach the ocean (Hosier et al. 1981).
Campfires and the use of flashlights on nesting beaches misorient hatchlings
and can deter nesting females (Mortimer 1979).
Recreational Beach Equipment: The placement of physical obstacles (e.g.,
lounge chairs, cabanas, umbrellas, Hobie cats, canoes, small boats and beach
cycles) on nesting beaches can hamper or deter nesting attempts and interfere
with incubating egg clutches and the sea approach of hatchlings. The
documentation of false crawls at these obstacles is becoming increasingly
common as more recreational beach equipment is left in place nightly on
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nesting beaches. Additionally, there are documented reports of nesting females
becoming entrapped under heavy wooden lounge chairs and cabanas on South
Florida nesting beaches (NMFS and FWS 1991). The placement of recreational
beach equipment directly above incubating egg clutches may hamper
hatchlings during emergence and can destroy eggs through direct invasion of
the nest (NMFS and FWS 1991).
Exotic Dune and Beach Vegetation: Non-native vegetation has invaded
many coastal areas and often outcompetes native species such as sea oats,
railroad vine, sea grape, dune panic grass, and pennywort. The invasion of less
stabilizing vegetation can lead to increased erosion and degradation of suitable
nesting habitat. Exotic vegetation may also form impenetrable root mats which
can prevent proper nest cavity excavation, invade and desiccate eggs, or trap
hatchlings. The Australian pine (Casuarina spp.) is particularly detrimental.
Dense stands of this species have taken over many coastal strand areas
throughout central and South Florida. Australian pines cause excessive shading
of the beach that would not otherwise occur. Studies in Florida suggest that
nests laid in shaded areas are subjected to lower incubation temperatures,
which may alter the natural hatchling sex ratio (Marcus and Maley 1987,
Schmelz and Mezich 1988). Fallen Australian pines limit access to suitable
nest sites and can entrap nesting females. Davis and Whiting (1977) reported
that nesting activity declined in Everglades National Park where dense stands
of Australian pine took over native beach berm vegetation on a remote nesting
beach. Conversely, along highly developed beaches, nesting may be
concentrated in areas where dense stands of Australian pines create a barrier to
intense beachfront and beach vicinity lighting (NMFS and FWS 1991).
Nest Loss to Abiotic Factors: Erosion or inundation and accretion of sand
above incubating nests appear to be the principal abiotic factors that may
negatively affect incubating egg clutches. While these factors are often widely
perceived as contributing significantly to nest mortality or lowered hatching
success, few quantitative studies have been conducted (Mortimer 1989). Studies
on a relatively undisturbed nesting beach by Witherington (1986) indicated that
excluding a late season severe storm event, erosion and inundation played a
relatively minor role in destruction of incubating nests. Inundation of nests and
accretion of sand above incubating nests as a result of the late season storm
played a major role in destroying nests from which hatchlings had not yet
emerged. Severe storm events (e.g., tropical storms and hurricanes) may result in
significant nest loss, but these events are typically aperiodic rather than annual
occurrences. In the southeastern U.S., severe storm events are generally
experienced after the peak of the hatching season and hence would not be
expected to affect the majority of incubating nests. Erosion and inundation of
nests are exacerbated through coastal development and shoreline engineering.
These threats are discussed above under beach armoring.
Predation: Predators, particularly exotics such as fire ants (Solenopsis
invicta); and human-associated ones including raccoons (Procyon lotor) and
opossums (Didelphis virginiana) are becoming increasingly detrimental to
nesting beaches.
Poaching: In the U.S., killing of female turtles is infrequent. However, in
a number of areas, egg poaching and clandestine markets for eggs are not
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GREEN SEA TURTLE
Table 2. Major green turtle nest survey/protection projects
in South Florida (1985-1990).
Beach length Number of Conservation
(km)
nests/year Measures
Project
uncommon. From 1983 to 1989, the Florida
Marine Patrol, DEP, made 29 arrests for
illegal possession of turtle eggs.
Disease
There is little information available to assess
Hutchinson Island
36.5
45-132
S
the comprehensive effects of disease and/or
parasites on wild populations of green sea
St. Lucie Inlet SP
3.8
7-17
S/SP
turtles. The vast majority of diseases and
Hobe Sound NWR
5.7
3-30
S/SP
conditions which have been identified or
Town of Jupiter Island
12.1
45-228
S
diagnosed in sea turtles are described from
captive stock, either turtles in experimental
J.D. MacArthur SP
2.9
9-65
S/SP
headstart programs or mariculture facilities
City of Boca Raton
5.6
2-43
S/NS/NR
(Wolke 1989). One notable exception is the
Broward County Beaches 39.0
4-106
S/NR
occurrence of fibropapillomatosis in the
green sea turtle, first described by Smith and
Miami-Dade Co. Beaches 22.5
3-11
S/NR
Coates (1938). Fibropapillomatosis is a
Wabasso Beach
8.0
14-55
S/PR
disease characterized by one or more nonNS=Nest Screening
NR=Nest Relocation
cancerous fibrous tumors, commonly located
PR=Predator Removal
S=Survey
on areas of soft skin. The tumors can be
debilitating and, in severe cases, fatal. They can result in reduced vision,
disorientation, blindness, physical obstruction to normal swimming and
feeding, an apparent increased susceptibility to parasitism by marine leeches,
and an increased susceptibility to entanglement in monofilament fishing line
(Balazs 1986). Blood counts and serum profiles of green turtles inflicted with
fibropapillomas indicate marked debilitation (Jacobson 1987).
Fibropapillomas are now common on immature green sea turtles in the central
Indian River system, Florida Bay, and in the Florida Keys (Ehrhart et al. 1986,
Witherington and Ehrhart 1987, Schroeder 1987a). In the central Indian River
lagoon, approximately half of all green sea turtles captured have been found to
bear papillomas of varying severity (Ehrhart et al. 1986). Fibropapillomas are
also commonly found on Hawaiian green turtles. Since 1989, incidence of this
disease at Kancohe Bay, Oahu, has ranged from 49 to 92 percent (Barrett
1996). Though green sea turtles collected in Puerto Rico and the U.S. Virgin
Islands have shown a very low occurrence of fibropapillomas (NMFS and
FWS 1991), recent reports from those areas indicate the incidence of disease is
greater.
Sebastian Inlet SRA
4.8
7-56
S/PR
Management
There are a number of management activities ongoing in South Florida to benefit
the green sea turtle. Table 2 lists some of the major Federal, State, and private nest
survey and protection projects in the South Florida Ecosystem. In addition to
management of coastal habitats, NMFS and FWS (1991) discuss additional
conservation measures for the green sea turtle in the marine environment.
Additional reviews of sea turtle conservation efforts in the southeastern U.S.
appear in Possardt (1991).
Conservation of sea turtle nesting habitat is continuing on several NWRs in
South Florida, including Archie Carr, Hobe Sound, Ten Thousand Islands, and the
Page
4-594
GREEN SEA TURTLE
complex of satellite refuges in the Florida Keys. Acquisition of high-density
nesting beaches between Melbourne Beach and Wabasso Beach, Florida, is
continuing to complete the Archie Carr NWR. Approximately 35 percent of the
green sea turtle nesting in the U.S. occurs along this 33 km stretch of beach. The
State of Florida purchased the first parcel specifically for the refuge in July 1990.
Federal acquisition began in 1991. When completed, the refuge will protect up to
16 km of nesting beach. Since the initial acquisition, Brevard County and the
Richard King Mellon Foundation have joined in as acquisition partners. Hobe
Sound NWR, located north of West Palm Beach in Martin County, contains 5.25
km of Atlantic coast shoreline for nesting habitat. In addition to providing some
of the most productive sea turtle nesting habitat in the U.S., the refuge is also
home to Florida scrub-jays (Aphelocoma coerulescens) and gopher tortoises
(Gopherus polyphemus). The most longstanding beach management program has
been to reduce destruction of nests by natural predators, such as raccoons. Control
of numerous exotic plants such as Australian pine and Brazilian pepper (Schinus
terebinthifolius) are also major issues in managing the refuge.
One of the most difficult habitat protection efforts throughout South Florida
is trying to minimize or eliminate the construction of seawalls, riprap, groins,
sandbags, and improperly placed drift or sand fences. State and Federal laws
designed to protect the beach and dune habitat in South Florida include the
Coastal Barrier Resources Act of 1982 and the Coastal Zone Protection Act of
1985. These have had varying degrees of success at maintaining suitable nesting
sites for sea turtles. Prior to 1995, DEP permits were required for all coastal
armoring projects prior to construction. When issuing these permits, DEP
incorporated sea turtle protection measures, and sea turtle concerns were generally
well addressed.
However, in 1995, the Florida Legislature passed a law giving coastal
counties and municipalities the authority to approve construction of coastal
armoring during certain emergency situations. (All non-emergency armoring
situations must still receive a DEP permit prior to construction.) Although the new
law weakened prior regulations on armoring, it does require that emergency
armoring structures approved by a coastal county or municipality be temporary
and that the structure be removed or a permit application submitted to DEP for a
permanent rigid coastal structure within 60 days after the emergency installation
of the structure. In addition, to implement this new law, DEP finalized a formal
agency rule on coastal armoring on September 12, 1996.
The new rule recommends that local governments obtain the necessary
approval from the FWS prior to authorizing armoring projects. The new rule also
requires that several measures be undertaken to address sea turtle concerns for
non-emergency armoring and for placement of permanent rigid coastal structures
subsequent to an emergency (temporary) armoring event. For example, the new
regulations require that (1) special conditions be placed on permitted activities to
limit the nature, timing, and sequence of construction, as well as address lighting
concerns; (2) structures not be used where the construction would result in a
significant adverse impact; and (3) armoring be removed if it is determined to not
be effective or to be causing a significant adverse impact to the beach and dune
system.
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GREEN SEA TURTLE
Beach nourishment is a better alternative for sea turtles than seawalls and
jetties. When beach nourishment was done mostly in the summer, all nests had
to be moved from the beach prior to nourishment. Now FWS and State natural
resource agencies review beach nourishment projects to ensure appropriate
timing of nourishment during the nesting and hatching season. In southwest
Floridas Gulf coast (Sarasota County through Monroe County), the green sea
turtle nesting and hatching season is from May 15 through October 31. In
southeast Floridas, Atlantic coast (Indian River County through Miami-Dade
County), the nesting and hatching season is from May 1 through November
30. Any management decisions regarding beach nourishment, beach armoring
and other coastal construction, marina and dock development, and artificial
lighting should consider these dates. Beaches where compaction after
nourishment is a problem are plowed to a depth of 92 cm to soften the sand so
that it is useable for nesting turtles (Nelson and Dickerson 1987). Progress is
being made toward better timing of projects and sand quality.
Progress is being made by counties and cities to prevent disorientation and
misorientation of hatchlings due to artificial lighting (Ernest et al. 1987,
Shoup and Wolf 1987). In South Florida, lighting ordinances have been passed
by Indian River, St. Lucie, Martin, Palm Beach, Broward, Monroe, Collier,
Charlotte, Sarasota and Lee counties, as well as numerous municipalities.
Most recently, Witherington and Martin (1996) provide a thorough discussion
of the effects of light pollution on sea turtle nesting beaches and on hatchling
and adult turtles. They also offer a variety of effective management solutions
for ameliorating this problem.
Information on the status and distribution of the green turtle is critical to
its conservation. Monitoring the various life stages of the turtles on nesting
beaches is being conducted to evaluate current and past management
practices. Data are collected on the number of nests laid, the number of nests
that successfully hatch, and the number of hatchlings that reach the ocean.
Standardized ground surveys on index beaches are underway throughout
Florida by the FWS, DEP, and by private groups and universities. Index
beaches include 80 percent of the nesting activity in Florida. Because of slow
growth rates and subsequent delayed sexual maturity, all monitoring will need
to be conducted over a long period of time to establish population trends.
Mortality of green sea turtles has been monitored since 1980 through the
implementation of a regional data collection effort. This voluntary stranding
network from Maine to Texas is coordinated by the NMFS and serves to
document the geographic and seasonal distribution of sea turtle mortality
(Schroeder 1987a,b). During 1987-89, four index zones were systematically
surveyed. It is clear that strandings represent an absolute minimum mortality.
However, they can be used as an annual index to mortality and are an
indication of the size and distribution of turtles being killed. They can also
provide valuable biological information on food habits, reproductive condition
and sex ratios.
Research is underway at NMFS in Honolulu and at the University of
Florida to determine the cause of the fibropapillomatosis disease affecting the
green sea turtle. Evidence of a herpes-like virus was found, but it is unclear
Page
4-596
GREEN SEA TURTLE
whether this is a primary or secondary infection. Management
recommendations to reduce the incidence and impact of this disease include
improving habitat quality in areas where occurrence is high, using strict
hygiene techniques when handling affected turtles, and minimizing
translocations of affected turtles (Barrett 1996).
Public support for sea turtle conservation efforts is essential for the longterm success of conservation programs. This is particularly true when
conservation measures are controversial or expensive. To heighten public
awareness and understanding of sea turtle conservation issues, a number of
educational activities and efforts are underway. For example, personnel
conducting turtle projects often advise tourists on what they can do to minimize
disturbance to nesting turtles, protect nests, and prevent hatchlings from being
disoriented. Many beaches have been posted with signs informing people of
the laws protecting sea turtles and providing either a local or a hotline number
to report violations.
Private conservation organizations such as the Center for Marine
Conservation, Greenpeace, and the National Audubon Society, as well as
Federal and State agencies have produced and distributed a variety of audiovisual aids and printed materials about sea turtles. These include: the brochure
Attention Beach Users, a booklet (Raymond 1984b) on the various types of
light fixtures and ways of screening lights to lessen their effects on hatchings,
Lights Out bumper stickers and decals, a coloring book, video tapes,
slide/tape programs, full color identification posters of the different species of
sea turtles, and a hawksbill poster. Florida Power and Light Company also has
produced a booklet (Van Meter 1990) and two leaflets with information on sea
turtles, as well as a coastal roadway lighting manual.
Page
4-597
GREEN SEA TURTLE
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Tritaik, P. 1998. Comments on technical/agency draft multi-species recovery plan for
South Florida. February 3, 1998.
U.S. Fish and Wildlife Service [FWS]. 1996. Hobe Sound National Wildlife Refuge,
1996 Sea turtle nesting report. On file at South Florida Ecosystem Office, U.S.
Fish and Wildlife Service; Vero Beach, Florida.
Van Meter, V.B. 1990. Floridas sea turtles. Florida Power and Light Company; Miami,
Florida.
Witherington, B.E. 1986. Human and natural causes of marine turtle clutch and
hatchling mortality and their relationship to hatchling production on an important
Florida nesting beach. Unpublished M.S. Thesis; University of Central Florida,
Orlando.
Witherington, B.E. 1992. Behavioral responses of nesting sea turtles to artificial
lighting. Herpetologica 48:31-39.
Witherington, B.E., and L.M. Ehrhart. 1987. A preliminary characterization of the
disease papillomatosis affecting green turtles at the Indian River lagoon system,
Florida. (Abstract). Seventh annual workshop on sea turtle biology and
conservation, March 1987; Wekiwa Springs State Park, Florida.
Witherington, B.E., and L.M. Ehrhart. 1989. Status and reproductive characteristics of
green turtles (Chelonia mydas) nesting in Florida. Pages 351-352 in L. Ogren, F.
Berry, K. Bjorndal, H. Kumpf, R. Mast, G. Medina, H. Reichart, and R. Witham,
eds. Proceedings of the second western atlantic turtle symposium. NOAA
Technical Memorandum NMFS-SEFC-226. On file at South Florida Ecosystem
Office, U. S. Fish and Wildlife Service; Vero Beach, Florida.
Witherington, B.E., K.A. Bjorndal, and C.M. McCabe. 1990. Temporal pattern of
nocturnal emergence of loggerhead turtle from natural nests. Copeia 1990:11651168.
Witherington, B.E., and K.A. Bjorndal. 1991. Influences of artificial lighting on the
seaward orientation of hatchling loggerhead turtles Caretta caretta. Biological
Conservation 55: 139-149.
Witherington, B.E., and R.E. Martin. 1996. Understanding, assessing, and resolving
light pollution problems on sea turtle nesting beaches. FMRI Technical Report
TR-2. Florida Marine Research Institute; St. Petersburg, Florida.
Wolke, R.E. 1989. Pathology and sea turtle conservation. Unpublished report.
Page
4-603
Page
4-604
Recovery for the
Green Sea Turtle
Chelonia mydas
Recovery Objective: DELIST the species once recovery criteria has been met.
South Florida Contribution: SUPPORT delisting actions.
Recovery Criteria
The South Florida recovery contribution parallels the existing recovery plans for the sea turtles. South
Floridas objective for the loggerhead turtle, green turtle, leatherback turtle and hawksbill turtle will be
achieved when: the level of nesting for each species is continuously monitored and increases to the speciesspecific recovery goal; beaches supporting greater than 50 percent of the nesting activity are in public
ownership; all important nesting beaches are protected and appropriately managed to prevent further
degradation; non-native nuisance species have been controlled or eliminated on public lands; at least 60
percent hatch success is documented on major nesting beaches; effective lighting ordinances or lighting
plans are implemented; and beaches are restored or rehabilitated to be suitable for nesting where appropriate.
Species-level Recovery Actions
S1.
Continue standardized surveys of nesting beaches. Nesting surveys are undertaken on the
majority of nesting beaches. In the past, beach coverage varied from year to year, as did the
frequency of surveys, experience and training of surveyors, and data reporting. Consequently,
no determination of nesting population trends had been possible with any degree of certainty.
However, in 1989, to better assess trends in nesting, DEP, in cooperation with FWS, initiated
an Index Nesting Beach Survey (INBS) program to collect nesting data that can be used to
statistically and scientifically analyze population trends. The INBS program should continue
to gather a long-term data base on nesting activities in Florida that can be used as an index of
nesting population trends.
S2.
Protect and manage populations on nesting beaches. Predators, poaching, tidal inundation,
artificial lighting and human activities on nesting beaches diminish reproductive success.
Monitoring of nesting activity is necessary to implement and evaluate appropriate nest
protection measures and determine trends in the nesting population.
S2.1.
Evaluate nest success and implement appropriate nest protection measures.
Nesting and hatching success and hatchling emerging success on beaches occurring
on State or Federal lands and all other important local or regional nesting beaches
should be evaluated. Appropriate nest protection measures should be implemented
Page
4-605
GREEN SEA TURTLE
by FWS and DEP, and appropriate local governments or organizations, to ensure
greater than 60 percent hatch rate. Until recovery is ensured, however, projects on
all Federal and State lands and key nesting beaches, such as those in Brevard, Indian
River, St. Lucie, Martin, and Palm Beach counties, should strive for a higher rate of
hatching success. In all cases, the least manipulative method should be employed to
avoid interfering with known or unknown natural biological processes. Artificial
incubation should be avoided. Where beach hatcheries are necessary, they should be
located and constructed to allow self release, and hatch rates approaching 90 percent
should be attained. Nest protection measures should always enable hatchling release
the same night of hatching.
S2.2.
Determine influence of factors such as tidal inundation and foot traffic on
hatching success. Tidal inundation can diminish hatching success, depending on
frequency, duration, and developmental stage of embryos. Some nests are relocated
due to the perceived threat from tides. The extent to which eggs can tolerate tidal
inundation needs to be quantified to enable development of guidelines for nest
relocation relative to tidal threats. The effect of foot traffic on hatching success is
unknown, although many beaches with significant nesting also have high public use.
FWS should support research and, in conjunction with DEP, develop
recommendations for nest protection from tidal threat and foot traffic.
S2.3.
Reduce effects of artificial lighting on hatchlings and nesting females. Studies
have shown that light pollution can deter female sea turtles from coming onto the
beach to nest; in fact, brightly lit beaches have been determined to be used less
frequently for nesting. Also, females attempting to return to sea after nesting can be
disoriented by beach lighting and have difficulties making it back to the ocean. In
some cases, nesting females have ended up on coastal highways and been struck by
vehicles. Artificial beach lighting is even more detrimental to hatchling sea turtles,
which emerge from nests at night. Under natural conditions, hatchlings move toward
the brightest, most open horizon, which is over the ocean. However, when bright
light sources are present on the beach, they become the brightest spot on the horizon
and attract hatchlings in the wrong direction, making them more vulnerable to
predators, desiccation, exhaustion, and vehicles.
S2.3.1.
Page
4-606
Implement and enforce lighting ordinances and resolve lighting
problems in areas where lighting ordinances have not been adopted.
FWS and DEP should identify and resolve artificial lighting impacts to
sea turtles in South Florida. Since 1987, hatchling disorientation incidents
observed by DEP marine turtle permit holders and park personnel have
been reported through standardized reporting forms. Report forms serve
as documentation for lighting problems on nesting beaches and allow the
identification of specific problem light sources. FWS and DEP should use
these report forms to locate and resolve lighting problems, with the help
of local governments, through public education efforts, and by directly
contacting the owners of the problem lights and making recommendations for their modification. FWS and DEP should also proactively
conduct pre-season lighting inspections to identify and make recommendations for correcting problem light sources before they result in
disorientation events.
GREEN SEA TURTLE
Where lighting ordinances have been adopted and enforced, hatchling
disorientation and misorientation have been drastically reduced. All
coastal counties and communities with nesting beaches should adopt
ordinances (March through October on the Atlantic Coast and May
through October on the Gulf Coast). Many incorporated communities
within Broward and Palm Beach counties, Florida, are particularly
problematic because of the high-density nesting beaches and the lack of
effective lighting regulations. DEP should ensure appropriate lighting on
new construction projects and ensure follow-up surveys to assess
continued compliance with lighting plans.
S2.3.2.
Evaluate extent of hatchling disorientation and misorientation on all
important nesting beaches. FWS, DEP, and counties should continue to
evaluate hatchling disorientation and misorientation problems on all
important nesting beaches. Many lighting ordinance requirements do not
become effective until 11 p.m., whereas over 30 percent of hatchling
emergence occurs prior to this time (Witherington et al. 1990). FWS,
DEP, and county governments should also support research to gather
additional quantitative data on hatchling emergence times and nesting
times on representative beaches throughout South Florida to support the
most effective time requirements for lighting ordinances.
S2.3.3.
Prosecute individuals or entities responsible for hatchling
disorientation and misorientation under the Endangered Species Act
or appropriate State laws. Hatchling disorientation and misorientation
from artificial lights can cause high mortality and be the major source of
hatchling mortality on some nesting beaches if not controlled. Law
enforcement efforts should be focused where lighting ordinances are not
being implemented or enforced on major nesting beaches and where
repeated violations are not corrected.
S2.4.
Ensure beach nourishment and coastal construction activities are planned to
avoid disruption of nesting and hatching activities. These activities can cause
significant disruption of nesting activities during the nesting season when viewed
cumulatively over the nesting range. Nest relocation can involve manipulation of
large numbers of nests, which can result in lowered hatch success and altered
hatchling sex ratios, and therefore is not an acceptable alternative to altering the
timing of projects during the peak nesting period. COE, FWS, and DEP should
ensure beach nourishment and other beach construction activities are not permitted
during the nesting season on important nesting beaches.
S2.5.
Ensure law enforcement activities eliminate poaching and harassment.
Poaching, while not a significant cause of nest loss regionally, is occasionally a local
problem. Poaching has been repeatedly reported around the Ten Thousand Islands
NWR and adjacent islands in southwest Florida. In addition, intentional and
unintentional disturbance and harassment of nesting turtles is an increasing problem
on many beaches. FWS should work closely with DEP to identify problem areas and
focus intensive law enforcement efforts to eliminate poaching and deter harassment
of nesting turtles.
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GREEN SEA TURTLE
S3.
Page
Continue to gather information on species and population biology.
S3.1.
Determine etiology of fibropapillomatosis. Research on the fibropapilloma disease
should be continued and expanded. Fibropapillomatosis (FP) is a disease of sea
turtles characterized by the development of multiple tumors on the skin and also internal
organs, most frequently the lungs and kidneys. The tumors interfere with swimming,
eating, breathing, seeing, and reproduction, and turtles with heavy tumor burdens
become severely debilitated and die. FP has seriously impacted green sea turtle
populations in Florida (about 50 percent of juvenile green turtles in Indian River
Lagoon and Florida Bay have fibropapillomas) and is now emerging as a significant
threat to the loggerhead as well. FP is a transmissible disease caused by a virus, and,
while both a unique herpesvirus and retroviruses have been identified in FP tumors,
neither has yet been proven to be the cause of the disease. Researchers are concerned
that there may be environmental (contaminant) cofactors for this disease in nearshore
areas. Continuation and expansion of research on the disease is essential to developing
an approach to remedying the problem.
S3.2.
Maintain the Sea Turtle Stranding and Salvage Network. Most accessible United
States beaches in the Atlantic and Gulf of Mexico are surveyed for stranded sea
turtles by volunteer or contract personnel. Through the Sea Turtle Stranding and
Salvage Network, stranding data are archived and summarized by the NMFS Miami
Laboratory. These data provide an index of sea turtle mortality and are thought to be
a cost-effective means of evaluating the effectiveness of the (Turtle Exclusion
Device) TED regulations. These data also provide basic biological information on
sea turtles and are useful in determining other sources of mortality. The systematic
stranding surveys of index areas need to be continued in South Florida. Periodic
review of the efficacy of surveys should also be conducted.
S3.3.
Centralize administration and coordination of tagging programs. Sea turtle
researchers commonly tag turtles encountered during their research projects, and
usually maintain independent tagging data bases. The lack of centralization for
administering these tagging data bases often results in confusion when tagged turtles
are recaptured, and delays in reporting of recaptures to the person originally tagging
the turtle. NMFS and FWS should investigate the possibilities of establishing a
centralized tagging data base, including Passive Integrated Transponder (PIT) tags.
4-608
S3.3.1.
Centralize tag series records. A centralized tag series data base is
needed to ensure that recaptured tagged turtles can be promptly reported
to persons who initially tagged the animal. The tag series data base would
include listings of all tag series that have been placed on sea turtles in the
wild, including the name and address of the researcher. This would
eliminate problems in determining which researcher is using which tag
series or types of tags, and would preclude unnecessary delays in
reporting of tag returns. NMFS and/or FWS should establish and
maintain this data base.
S3.3.2.
Centralize turtle tagging records. In addition to the need for a
centralization of tag series records, there are advantages in developing a
centralized turtle tagging data base. Such a data base would allow all
turtle researchers to trace unfamiliar tag series or types to their source,
and also to have immediate access to important biological information
GREEN SEA TURTLE
collected at the time of original capture. The major disadvantage is that
this data base would require frequent editing and updating, and would be
costly and somewhat time consuming to maintain. It would also make it
possible for unethical researchers to exploit the work of others, while
providing no guarantees that such contributions would be acknowledged.
NMFS and FWS should determine whether such a data base can be
established and is feasible to maintain.
S3.4.
Develop requirements for care and maintenance of turtles in captivity,
including diet, water quality, tank size, and treatment of injury and disease. Sea
turtles are maintained in captivity for rehabilitation, research, or educational display.
Proper care will ensure the maximum number of rehabilitated turtles can be returned
to the wild and a minimum number removed from the wild for research or education
purposes. None of these requirements has been scientifically evaluated to determine
the best possible captive conditions for sea turtles. FWS and NMFS should support
the necessary research to develop these criteria, particularly relating to diet and the
treatment of injury and disease. These criteria should be published and required for
any permit to hold sea turtles in captivity. FWS, NMFS and/or DEP should inspect
permitted facilities at least annually for compliance with permit requirements.
S4.
Monitor trends in nesting activity. DEP and FWS should continue to refine standardized nest
survey criteria, identify additional index survey beaches to be monitored, and continue to conduct
training workshops for surveyors. Consequently, DEP and FWS should ensure that routine
monitoring of nesting beaches is done on at least a weekly basis during the time that green turtles
are nesting, including the timeframes of any nesting that occurs outside of the regular survey
period.
S5.
Continue information and education activities. Sea turtle conservation requires long-term
public support over a large geographic area. The public must be factually informed of the
issues, particularly when conservation measures conflict with human activities, such as
commercial fisheries, beach development, and public use of nesting beaches. Public education
is the foundation upon which a long-term conservation program will succeed or fail.
S5.1.
Update existing slide programs and information leaflets on sea turtle
conservation for the general public. FWS has developed a bi-lingual slide tape
program on sea turtle conservation and should keep the program current and
available for all public institutions and conservation organizations. FWS and DEP
should continually update and supply the public with informational brochures on sea
turtle ecology and conservation needs.
S5.2.
Disseminate information from brochures and reports on recommended lighting
modifications or measures to reduce hatchling disorientation and misorientation.
Recently published literature contains information on the types of light, screening or
shading that is best for turtles (e.g., Witherington and Martin 1996).
S5.3.
Develop public service announcements (PSA) regarding the sea turtle artificial
lighting conflict, and disturbance of nesting activities by public nighttime beach
activities. A professionally produced public service announcement for radio and TV
would provide tremendous support and reinforcement of the many coastal lighting
ordinances. It would generate greater support through understanding. FWS and DEP
should develop a high quality PSA that could be used throughout the Southeast
during the nesting season.
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GREEN SEA TURTLE
S5.4.
Ensure facilities permitted to hold and display captive sea turtles have
appropriate informational displays. Over 50 facilities are permitted to hold sea
turtles for rehabilitation, research, and public education. Many are on public display
and afford opportunities for public education. Display of accurate information on the
basic biology and conservation problems of sea turtles should be a requirement of all
permittees. All facilities should be visited by FWS, NMFS and/or DEP to ensure
captive sea turtles are being displayed in a way to meet these criteria.
S5.5.
Post informational signs at public access points on nesting beaches. Public
access points to nesting beaches provide excellent opportunities to inform the public
of necessary precautions for compatible public use on the nesting beach and to
develop public support through informational and educational signs. FWS, NPS,
DEP and other appropriate organizations should post such educational and
informational signs on nesting beaches as appropriate.
Habitat-level Recovery Actions
H1.
Protect and manage nesting habitat. Coastal development has already destroyed or
degraded many miles of nesting habitat in South Florida. Although sea turtle nesting occurs
on over 2,240 km of beaches within the southeast United States, development pressures are so
great that cumulative impacts could result in increased degradation or destruction of nesting
habitat and eventually lead to a significant population decline if not properly managed.
H1.1.
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4-610
Ensure beach nourishment projects are compatible with maintaining good
quality nesting habitat. Beach nourishment can improve nesting habitat in areas of
severe erosion and is a preferred alternative to beach armoring. However, placement
of sand on an eroded section of beach or an existing beach in and of itself may not
provide suitable nesting habitat for sea turtles. Although beach nourishment may
increase the potential nesting area, significant negative impacts to sea turtles may
result if protective measures are not incorporated during construction.
H1.1.1.
Evaluate sand transfer systems as an alternative to beach
nourishment. Sand transfer systems can diminish the necessity for
frequent beach renourishment and thereby reduce disruption of nesting
activities and eliminate sand compaction. The construction and operation
of these systems must be carefully evaluated to ensure important
nearshore habitats are not degraded or sea turtles injured or destroyed.
H1.1.2.
Refine a sand budget formulation methodology for Sebastian Inlet.
Inlets interrupt the natural flow of longshore sediment transport along the
shoreline. The interrupted flow of sand is diverted either offshore in ebb
tide shoals, into bays or lagoons in flood tide shoals, or in navigation
channels (National Research Council 1990). As a result, erosion occurs
downdrift of the interrupted shoreline. There are six man-made inlets on
the Atlantic coast from Indian River County to Broward County. In Indian
River County, for example, erosion has been nearly 2 m per year at
Sebastian Inlet SRA (just south of Sebastian Inlet), when the average
erosion rate for the county is just under .3 m per year (J. Tabar, Indian
River County, personal communication 1996). DEP, Sebastian Inlet Tax
District, and Indian River County should conduct engineering studies to
refine a sand budget formulation methodology for the Sebastian Inlet.
GREEN SEA TURTLE
Other needs include: annually bypassing sand to downdrift beaches,
conducting further studies of the long-term effects of the flood shoal on
the inlet-related sediment budget, identifying the long-term impacts of
sand impoundments and sediment volume deficit to downdrift areas, and
determining the area of inlet influence.
H1.2.
H1.3.
Prevent degradation of nesting habitat from seawalls, revetments, sand bags, sand
fences, or other erosion control measures. One of the most difficult habitat protection
efforts throughout South Florida is trying to minimize or eliminate the construction of
seawalls, riprap, groins, sandbags, and improperly placed drift or sand fences. In 1995,
the Florida Legislature passed a law giving coastal counties and municipalities the
authority to approve construction of coastal armoring during certain emergency
situations. (All non-emergency armoring situations must still receive a DEP permit prior
to construction.) Although the new law weakened prior regulations on armoring, it does
require that emergency armoring structures approved by a coastal county or
municipality be temporary and that the structure be removed, or a permit application
submitted to DEP for a permanent rigid coastal structure, within 60 days after the
emergency installation of the structure. In addition, to implement this new law, DEP
finalized a formal agency rule on coastal armoring on September 12, 1996.
H1.2.1.
Ensure laws regulating coastal construction and beach armoring are
enforced. The 1996 DEP rule recommends that local governments obtain
an incidental take permit from FWS under section 10 of the Endangered
Species Act and develop a sea turtle habitat conservation plan prior to
authorizing armoring projects. The new rule also requires that several
measures be undertaken to address sea turtle concerns for non-emergency
armoring and for placement of permanent rigid coastal structures
subsequent to an emergency (temporary) armoring event. For example,
the new regulations require that (1) special conditions be placed on
permitted activities to limit the nature, timing, and sequence of
construction, as well as address lighting concerns; (2) structures not be
used where the construction would result in a significant adverse impact;
and (3) armoring be removed if it is determined to not be effective or to
be causing a significant adverse impact to the beach and dune system.
H1.2.2.
Ensure failed erosion control structures are removed. Failed erosion
control structures such as uncovered plastic bags or tubes and fragmented
concrete or wooden structures degrade nesting habitat and deter nesting
activities. DEP should ensure failed structures are removed from nesting
beaches.
H1.2.3.
Develop standard requirements for sand fence construction. Sand
fences can effectively build dune systems and improve nesting habitat;
however, improperly designed sand fences can trap nesting females or
hatchlings and prevent access to suitable nesting habitat. DEP and FWS
should develop and evaluate sand fencing designs and establish standard
requirements for sand fence construction.
Identify important nesting beaches experiencing greater than 40 percent nest loss
from erosion and implement appropriate habitat restoration measures (without
relocation). Some important nesting beaches now suffer severe erosion as a result of
Page
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GREEN SEA TURTLE
inlet maintenance or jetty construction. In some situations, limited safe locations for
relocating nests place constraints on nest relocation programs. Nest relocation programs
should be considered as a short-term measure at best to protect nests in these situations,
with primary efforts directed toward habitat restoration. DEP and FWS should review
all important nesting beaches and identify those with 40 percent or more nest loss due
to erosion or tidal inundation. Habitat restoration plans should be developed and
implemented for identified nesting beaches.
H1.4.
Acquire or otherwise ensure the long-term protection of important nesting
beaches. Acquisition of important sea turtle nesting beaches would ensure long-term
protection of U.S. nesting habitat. Acquisition and protection of undisturbed nesting
habitat would enhance sea turtle nesting and hatching success.
H1.4.1.
Continue to acquire in fee title all undeveloped beaches between
Melbourne Beach and Wabasso Beach, Florida, for the Archie Carr
National Wildlife Refuge. The Archie Carr NWR was designated by
Congress in 1989 in recognition of the need for long stretches of quiet,
undisturbed sandy beaches, with little or no artificial lighting, to ensure the
reproductive success and survival of sea turtles. The refuge is located within
a 33-km stretch of beach on the barrier islands of Brevard and Indian River
counties on the Atlantic coast of Florida. Approximately 30 to 35 percent of
all green sea turtle nesting in the U.S. occurs along this stretch of beach. The
proposed acquisition plan for the refuge set a goal for purchase of 15 km
within four sections of this 33-km stretch. Three of the sections are located
in Brevard County and one in Indian River County.
Partners in the land acquisition effort for the refuge and adjacent buffer areas
on the barrier island include FWS, DEP, Brevard County, Indian River
County, Richard King Mellon Foundation, The Conservation Fund, and The
Nature Conservancy. To date, contributions from the State of Florida and
local county partnerships account for over 70 percent of land acquisition
expenditures, while contributions from the Richard King Mellon Foundation
account for over 21 percent of acquisition costs for lands on the barrier
island. Federal acquisition efforts account for about 8 percent of purchases
to date.
About 61 percent of the available beachfront acquisitions for the Refuge
have been completed. Of the original 15 km of beachfront identified for
acquisition, approximately 8 km have been acquired and 5 km are awaiting
purchase. The remaining lands have been purchased for private
development and are no longer available. Escalating coastal development in
Brevard and Indian River counties threatens the remaining parcels identified
for acquisition. Ongoing development continues to fragment the remaining
habitat and could result in increased lighting and beach armoring, which
negatively impact sea turtles. A narrow window of opportunity is left to
acquire the last remaining lands required for the refuge.
H1.4.2.
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Evaluate the status of the high-density nesting beaches on Hutchinson
Island, Florida, and develop a plan to ensure its long-term protection.
Approximately 10 percent of green sea turtle nesting in the United States
GREEN SEA TURTLE
occurs along this 32 km beach. Development is degrading nesting habitat,
and public use is causing significant disturbance to nesting activities. DEP
and FWS should evaluate the threats and take appropriate measures,
including acquisition, to ensure long-term protection.
H1.4.3.
H2.
H3.
Evaluate status of other undeveloped beaches that provide important
habitat for maintaining historic nesting distribution and develop a plan
for long-term protection. DEP and FWS should evaluate other nesting
beaches in the Southeast that contribute significantly to the historic nesting
distribution to ensure long-term protection.
Restore areas to suitable habitat.
H2.1.
Reestablish dunes and native vegetation. Dune restoration and revegetation with
native plants should be a required component of all renourishment projects. This will
enhance beach stability and nesting habitat and may result in the need for less frequent
renourishment activities.
H2.2.
Remove exotic vegetation and prevent spread to nesting beaches. Australian pine
trees shade nests and can alter natural hatchling sex ratios. Australian pines also
aggressively replace native dune and beach vegetation through shading and chemical
inhibition and consequently exacerbate erosion and loss of nesting habitat. Erosion can
topple trees and leave exposed roots that can entrap nesting females. Removal of
exotics, such as is ongoing at St. Lucie Inlet SP, Hobe Sound NWR, and Dry Tortugas
NP, Florida, should continue. DEP, FWS, and NPS should identify other important
nesting beaches where exotic vegetation is degrading nesting habitat and work with
responsible parties to restore natural vegetation.
Conduct research to evaluate the relationship of sand characteristics (including aragonite)
and female nesting behavior, nesting success, hatching success, hatchling emerging success,
hatchling fitness, and sex ratios. Beach nourishment may result in changes in sand density
(compaction), beach shear resistance (hardness), beach moisture content, beach slope, sand color,
sand grain size, sand grain shape, and sand grain mineral content if the placed sand is dissimilar
from the original beach sand. These changes could result in adverse impacts on nest site selection,
digging behavior, clutch viability, and emergence by hatchlings. Gas diffusion of nests could be
affected by sand grain shape, size, and compaction and variations may alter hatching success.
Sand color and moisture influence nest incubation temperature and can affect hatchling sex
determination. The effect of importing non-native materials, such as aragonite, to U.S. beaches
for beach nourishment adds additional unknowns that could conceivably affect female nesting
behavior, nesting success, hatching success, hatchling emerging success, hatchling fitness, and
sex ratios and should be fully evaluated before large-scale use.
Studies of alternative sand sources for beach renourishment and their suitability for sea turtles are
needed. After years of beach renourishment, Miami-Dade County is running out of suitable sand
material for future renourishment projects. Broward and Palm Beach counties will also be running
out of sand sources in the near future. COE is exploring the potential use of sand from upland sand
sources and the importation of sand from the Bahamas and the Turks and Caicos Islands.
Concerns have been raised about the long-term consequences to nesting and incubating sea turtles
using these alternative beach renourishing materials. In order to adequately address these
concerns in section 7 consultations, studies must be conducted on the suitability of these materials
prior to receiving a proposal for large-scale nourishment of Florida beaches with these alternative
sand sources.
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T Green Sea Turtle Chelonia mydas

Transcription

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